A grade three medial collateral ligament (mcl) strain in his left knee and badly torn adductor (groin) muscles mean his Chiefs season is almost certainly over and he probably won't get to play for Counties Manukau in the NPC either.

He was still awaiting the final analysis of the MRI scan he had on his knee on Wednesday when spoken to yesterday, but neither he nor head coach Dave Rennie held out much hope of him being able to take part in the Super Rugby playoffs.

"My groin has been an ongoing thing for the last two years and I think it has reached its end and it's probably a pretty good time to get it all fixed up and get the knee done as well."

But the timing could have been better for the 24-year-old fullback/winger who this year turned himself into an elusive centre in the absence of the injured Richard Kahui.

"It's come at a bad time to be honest. I wish I did it in a final or something like that but I guess that's just rugby, that's the way it is, you get the ups and downs so I guess I've just got to prepare myself for next year now," Nanai-Williams said.

The knee injury occurred in the 26-16 win over the Blues at Eden Park last Saturday when a couple of forwards fell on him while he was trapped in a ruck.

"It sort of just got bent right underneath. I got up out of the ruck and felt quite wobbly, but I got the physio to just strap it so I could keep running.

"I thought it would be all right but didn't figure till after the game that it wasn't all right.

"I think I did more damage by keeping on playing on it. I knew [at the time] it was sore and I knew it was kind of bad but just wanted to keep playing for the boys to make sure we got that win."

Nanai-Williams said both his adductor muscles were almost torn completely away from the bone and he had been running on energy and adrenalin.

"With all the stepping and stuff it's the main muscle that gets you swerving and things so I'm actually lucky I've played this long with that pain."

He had always planned to get them surgically repaired after the rugby season but now that has been brought forward.

Meanwhile, Rennie has come up with a unique process for deciding who will make up his backline in Nanai-Williams' absence for next weekend's Super Rugby home semi-final with Bundee Aki, Andrew Horrell and Charlie Ngatai the leading midfield candidates.